Order Organocuprates Research Articles

Synthesis of Highly Enantioenriched Chiral α-Aminoorganotins via Diastereoselective Ring Opening of ChiralN-(Arenesulfonyl) 2-Tributylstannyloxazolidines

trans-N-(Arenesulfonyl)-2-tributylstannyloxazolidines derived from (R)-phenylglycinol were diastereoselectively ring-opened by soft organometallic reagents in the presence of BF(3).OEt(2). Both higher order organocuprates and allyltributyltin afforded the desired products in good-to-excellent yields and high diastereoselectivities (dr up to 99/1). The stereochemical assignments of tributylstannyl-beta-aminoalcohols were firmly established from NMR data and after determination of several radiocrystallographic structures. Mechanisms were proposed in order to rationalize the observed selectivities.

Stereoselective α‐Amidoalkylation Reactions of Phenylglycinol‐Derived Bicyclic Lactams.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Stereoselective α-amidoalkylation reactions of phenylglycinol-derived bicyclic lactams

The stereochemical outcome of α-amidoalkylation reactions from the chiral non-racemic bicyclic lactams trans- 1 and cis- 1 using indole, allyltrimethylsilane, higher order organocuprates, TMSCN, and Grignard reagents is discussed.

A new route to 2-alkenyl-1,3-dicarbonyl compounds, intermediates in the synthesis of dihydrofurans

A two step synthetic strategy for obtaining 2-alkenyl-1,3-dicarbonyl compounds from the corresponding 1,3-dicarbonyl compounds is reported. The method is based on a Knoevenagel condensation and a Michael addition using a high order organocuprate procedure, and proves to be of general value. Obtained compounds are useful starting materials for the synthesis of furan derivatives.

A Synthesis of (3S*,4R*)-Luffariolide

A 1,2-metallate rearrangement of a higher order organocuprate was a key step in the synthesis of a trisubstituted alkene in the marine sesterterpenoid Luffariolide E. The synthesis shows that the stereochemistry of Luffariolides C, D, and E is (3S,4R).

Diastereoselective Amidoalkylation Reactions of Electrochemically Methoxylated Chiral 2-Oxazolidinones with Organocopper Reagents

(4S,4R)-4-Methoxy-5-methyl-2-oxazolinone (2ab), easily obtained by electrochemical decarboxylative methoxylation of the cyclic L-threonine derivative (4S,5R)-5-methyl-2-oxazolidinone-4-carboxylic acid (1), acts as effective diastereoselective amidoalkylation reagent. The methoxy group exchange in 2ab can be performed with higher order organocuprates (R 3 Cu 2 Li) in the presence of BF 3 .OEt 2 . The 4-alkyl- or 4-aryl-substituted 2-oxazolidinones 9-6 can be obtained with trans diastereoselectivities between 75 and 98% in S N 1 fashion via the intermediate N-acylimine. On the contrary, the N-methylated (4RS,5R)-4-methoxy-3,5-dimethyl-2-oxazolidinone (7ab) undergoes methoxy group exchange under identical conditions mainly via the S N 2 mechanism. Thus, starting from trans-7a mainly cis-8b is formed with 76% ds. The described procedures make cis- or trans-4-alkyl-5-methyl-2-oxazolidinones and the respective dichiral 2-amino alcohols selectively available by a short reaction sequence

Nonracemic frontalin via copper- and palladium-based skeletal construction and the asymmetric dihydroxylation

The new higher order organocuprate, Li 2 Cu(CN)(C(OMe):CH 2 ) 2 , prepared through a Sn→Li→Cu trans-metalation sequence, was found to efficiently couple with allyl bromide producing 2-methoxy-1,4-pentadiene (3) which is efficiently converted to the ketal 4. Hydroboration of 4 with 9-BBN-H and the selective oxidation of this adduct with trimethylamine N-oxide (TMANO) produces 9-oxa-10-borabicyclo[3.3.2]decane 5, which undergoes Pd-catalyzed cross coupling with 2-bromopropene producing 6, thereby accomplihing the construction of the frontalin carbon skeleton in 63% overall yield from allyl bromide.

ChemInform Abstract: Vicinal Epoxymesylates: Substrates for Iterative Organocuprate Chemistry.

AbstractReacting vicinal epoxymesylates with higher order and also with mixed higher order organocuprates is very selective for attack at the least hindered epoxide center.

ChemInform Abstract: Regioselective SN′ Allylic Substitution versus 1,4-Addition. Synthesis of α-Substituted β,γ-Unsaturated Esters.

The reaction of the higher order organocuprate reagents R2Cu(CN)Li2-BF3 with γ-bromo α,β-unsaturated esters gives with very high selectivity α-substituted β,γ-unsaturated esters arising from a SN′ allylic substitution. This reaction allows an easy access to α-silyl β,γ-unsaturated esters.

Vicinal epoxymesylates: substrates for iterative organocuprate Chemistry

Abstract Reacting vicinal epoxymesylates of general structure i with higher order and mixed higher order organocuprate reagents is shown to be very selective for attack at the least hindered epoxide center. The iterative application of this reaction - a sequence which consists of cuprate opening of epoxide i, reformation of an epoxide (I→ii), and subsequent cuprate opening of this intermediate epoxide (ii→iii) - provides ready access to acyclic carbon frameworks with up to three contiguous stereogenic centers.

ChemInform Abstract: The Role of BF3·Et2O in Reactions of Lower Order (Gilman) Organocuprates.

AbstractThe effects of BF3·Et2O on low order organocuprate reactions in THF are investigated so as to determine what factors are responsible for the oftentimes dramatic reaction‐rate enhancements observed.

The role of boron trifluoride etherate in reactions of lower order (Gilman) organocuprates

The role of boron trifluoride etherate in reactions of lower order (Gilman) organocuprates

Regioselective SN′ allylic substitution versus 1,4-addition: Synthesis of α-substituted β,γ-unsaturated esters

The reaction of the higher order organocuprate reagents R2Cu(CN)Li2-BF3 with γ-bromo α,β-unsaturated esters gives with very high selectivity α-substituted β,γ-unsaturated esters arising from a SN′ allylic substitution. This reaction allows an easy access to α-silyl β,γ-unsaturated esters.

ChemInform Abstract: Effects of BF3·Et2O on Higher Order Organocuprate Reactions: Substrate Activation or Cuprate Modification?

AbstractIn order to get insight into addition reactions of high order organocuprates in the presence of an additive, the reaction of the cuprate (I) under the influence of various additives is investigated.

Effects of boron trifluoride etherate on higher order organocuprate reactions: substrate activation or cuprate modification?

Effects of boron trifluoride etherate on higher order organocuprate reactions: substrate activation or cuprate modification?

The preparation of the first α-vinylidenepenams

Abstract Benzyl esters of the first 6-vinylidenepenams have been prepared by reaction of 6-position propargylic triflates with higher order organocuprates. This methodology permits a great deal of versatility in the introduction of substituents at the terminal allenyl position.

Reactions of higher order cyanocuprates derived from 2-lithiated furans: scope, limitations, and synthetic utility

A general study on the chemistry of higher order organocuprates derived from 2-lithiated furans with enones, epoxides, aldehydes and halides is described.

Organocuprate chemistry of vicinal epoxymesylates

Abstract Vicinal epoxymesylates are shown to react regiospecifically with higher order organocuprates in a stepwise manner allowing for the isolation of either mono- or bis-adducts.

Addition–elimination reactions of β-oxygenated vinyl sulphones

Stereoselective reaction of enol pivalate (3) with a variety of higher order organocuprate reagents gives vinyl sulphones in excellent yield.

Reaction of 8,8-dibromobicyclo[5.1.0]octanes with higher-order organocuprates.

Treatment of 8, 8-dibromobicyclo [5.1.0] octanes (A) with a higher order organocuprate prepared from cuprous thiocyanate (method A) or cuprous cyanide (method B) and methyllithium, followed by the addition of methyl iodide in situ, readily afforded 8, 8-dimethylbicyclo [5.1.0] octanes (B) in good yields. The results are summarized in Table I. Interestingly, reaction of the cisdibromides (4 and 19) under the present conditions gave tricyclic compounds (15 and 16, and 20, respectively)